The present invention is directed to a manually operated drilling and chipping tool including a striker mechanism and a tool bit holder. The striker mechanism delivers axially directed blows through an anvil to a tool bit clamped in the holder. The anvil has at least one recess into which a locking element can be positioned by a shifting member operable from the outside by a actuation member.
In a hammer drill disclosed in DE-PS 3 627 869 the blocking of blows by a pneumatic striker mechanism is achieved by hook shaped elements shiftable into a recess of a striking member. The striking member is thus held in an end position where it can not deliver blows to the tool bit.
The hook shaped elements are movable in the radial direction. An actuation device operable from the outside includes an eccentric deformation in the radial direction in its interior circumferential region, so that the axial stroke of a pin shaped element can be controlled. Accordingly, axial movement of the pin shaped element can be achieved by turning the actuation device in the circumferential direction, whereby the pin shaped element controls the radial movement of the hooked shaped elements. Since the striking member can be locked only in its leading position, it must be designed so that it can press the hooked shaped elements which are biased by spring means in the radial direction. The elements are displaced radially apart over an inclined plane, so that the inclined plane can drop into a recess in the striking member following on the inclined plane. As a result, the striking member can be locked only when it is moved by the striking mechanism in the working or operational direction.